The provincial police chief, Akhtar Hayat, said on Monday that the explosions rocked a counter-terrorism office in northwestern Swat Valley. The valley was previously controlled by militants before they were forced out in a military operation in 2009.
The official said in a statement that the blasts occurred after ammunition in the depot caught fire, adding that the fire was "most probably due to an electric short-circuit and no evidence of an attack from outside has been established so far."
Hayat said most of those killed in the blasts were police counter-terrorism officers, adding that a woman and her child who were passing by the building were also killed.
The explosions leveled the specialist counter-terrorism station in Kabal town of Swat Valley, in the northwestern region of Khyber Pakhtunkhwa, which neighbors Afghanistan.
Meanwhile, Khalid Sohail, the regional chief of the counter-terrorism department, told reporters that the explosions did not appear to be a suicide attack or other acts of terrorism.
"There was a store where we had a huge quantity of weapons, and until now we believe that there might have been some blast in it due to some carelessness," he said, adding, "We are keeping all our options open."
Sohail said the shock waves that followed the blasts caused "the complete collapse of the building."
Head of Swat police Shafi Ullah Gandapur also told reporters that a short-circuit in a basement storing "grenades and other explosives" was the cause of the blasts.
"There is no suggestion that it was caused by an outside attack or by suicide bombers," he added.
A hospital administration said it received several wounded people for treatment, some of them in critical condition.
MNA/PR